1. Field of the Invention
The present invention relates to high strength low drag tethers and systems using such tethers.
2. Description of Related Art
Some airborne wind energy systems, powered kites, tethered tidal power systems, moored platforms, tethered aerostats, and other tethered devices require high tether strength, significant tether power transmission, and are also sensitive to the effects of fluid-dynamic drag.
In the case of some airborne power generation systems, an aerial platform such as an airfoil may support an array of turbine driven generators. The platform may be linked to the ground with a tether which provides both the physical coupling as well as the electrical coupling of the tethered platform to the ground. In such a case, the electrical power generated by the turbine driven generators may travel along the tether from the aerial platform to the ground. In the case wherein the turbine driven generators also function as motor driven propellers, such as may be used when the platform is raised from the ground, the tether may provide electric power to the aerial platform. Also, the tether may be the conduit for telemetry related to control functions on the platform.
In addition, the tether provides the mechanical linkage of the platform to the ground. In the case of cross wind flying scenarios, such as when the aerial platform may be flying in patterns wherein the platform the apparent wind is much higher than the nominal actual wind speed, the drag of the tether may play a significant role in overall system function. Typically, the tether is wound on a reel of some sort either for storage of as part of the mechanical winching of the aerial platform.
What is called for is a tether, and system using a tether, that provides high strength for the support of an aerial platform from the ground. What is also called for is a tether that is low in drag such that it is suitable for support of airborne platforms.